Guidance

Glossary

Glossary

Average speed technology

Cameras with automatic number plate reading (ANPR) digital technology, placed in multiple locations (at least 2, at a minimum of 200 m apart) along a stretch of road to monitor a vehicle's average speed.

Daily Air Quality Index

A number used by government agencies to tell the public how polluted the air is or will be. The number is provided with recommended actions and health advice. The index is numbered 1 to 10 and divided into 4 bands: low (1 to 3), moderate (4 to 6), high (7 to 9) and very high (10).

Euro standards

Standards produced by EU Directives specifying maximum permitted emissions of various air pollutants. Light duty vehicle standards are referred to using Arabic numerals (Euro 1 to 6); standards for heavy duty vehicles use Roman numerals (Euro I to VI).

PM2.5, PM10

Particulate matter is produced by, among other things, combustion of fossil fuels or abrasion of tyres and brakes. Particles are classified by size, described using the abbreviation PM with a suffix (commonly 2.5 or 10) that gives the maximum particle size in micrometres. The mass concentration of particles is usually expressed in micrograms per m3 of air.

Airborne PM10 and PM2.5 come from both primary emissions (including combustion of fossil fuels, tyre and brake wear) and secondary particles (for example, nitrates and sulphates) formed when pollutants react in the atmosphere. PM2.5 particles are sometimes referred to as 'fine particles', and PM2.5–10 as 'coarse particles'. Fine particles can penetrate deep into the lungs.

Street ventilation

Air in a street flows in a pattern determined by many factors, including the shape and design of buildings. It mixes with air from outside the street. If there are sources of pollution in the street (primarily motor vehicles) the air flow is restricted.

Telematics

Technologies that store and send information on the speed, position, acceleration and deceleration of road vehicles. This, together with global positioning system (GPS) data, can be used to compare driving styles and estimate the impact on fuel consumption, emissions or wear and tear.

Travel plans

Travel plans are a way of assessing and then mitigating the potential negative effects that new developments could have on air pollution by generating significant amounts of motor traffic.